Alignment Mark Slotting for IC Singulation Yield
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Solution Overview
Problem
The existing alignment mark designs in integrated circuits create separation issues during the singulation process of dies from a wafer, leading to difficulties in precise separation and reduced die yield due to the length of alignment marks exceeding 300 μm.
Innovation Solution
The introduction of a slot etched along the longitudinal axis of the alignment structure within the metal layers on selected scribe lines facilitates easier separation by dividing the metal layers and metal-filled vias, allowing for precise cutting and separation during the singulation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If alignment marks are made long (exceeding 300 μm) to ensure precise layer alignment during fabrication, then measurement precision and manufacturing precision are improved, but separation difficulty increases during the singulation process
Solution Approach 1:
The alignment mark structure is segmented into multiple metal layers (first metal layer, second metal layer, third metal layer) with the slot etched through at least one of these layers. This segmentation allows the alignment mark to maintain its longitudinal extent for precise alignment while the slot creates separation points that facilitate easy die separation during singulation.
2Manufacturing precision
If alignment marks are made long (exceeding 300 μm) to ensure precise layer alignment during fabrication, then manufacturing precision is improved, but die yield decreases due to separation issues
Solution Approach 1:
The alignment mark is divided into multiple metal layers with slots etched through them, creating separation pathways that prevent separation failures during singulation. This maintains manufacturing precision while reducing defects that would otherwise lower die yield.
Solution Approach 2:
The slot is extracted as a separate feature from the continuous alignment mark structure, removing the problematic continuous metal path that causes separation issues while preserving the alignment functionality through the remaining metal layer structure.
3Manufacturing precision
If traditional continuous alignment mark structures are used, then manufacturing precision is maintained, but separation difficulty increases during singulation
Solution Approach 1:
The continuous alignment mark is segmented into discrete metal layers with slots between them, reducing the harmful resistance to separation while maintaining the precision alignment function through the layered structure.
Solution Approach 2:
The slot is introduced locally at specific positions within the alignment mark structure (through at least one metal layer) to reduce separation resistance only where needed, while preserving the continuous alignment function in other regions.
Data Source
AI summary
A photo alignment structure is provided that includes a wafer having scribe lines defined therein in a top planar surface of the wafer. An alignment structure is disposed on a top planar surface of the wafer longitudinally aligned with a portion of selected scribe lines, where the alignment structure is comprised of metal layers. A slot is defined along a longitudinal axis of the alignment structure in at least one of the metal layers.